Ruby; what's the "true" CR? - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 91 Old 02-01-2006, 06:41 AM - Thread Starter
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Well, we know about the measured 16700:1 that Greg got with iris in auto. But if we should compare these numbers with a projector with native CR, how much would that be? Would a 8000:1 native PJ give as good CR in dark scenes as the Ruby, or are the "true" CR of the Ruby higher?
Any way to measure this?`

And what does really Darin's iris tweaks do? Just lowering black level, or will it give a better CR in low level scenes?


/Mattias

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post #2 of 91 Old 02-01-2006, 07:03 AM
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This has been reported many times.

3000:1 iris open
5000:1 iris closed
15000:1 auto
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post #3 of 91 Old 02-01-2006, 07:19 AM
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I tried Darins tweaks and I noticed an improvement in overall picture quality. I havent measure the numbers per say. Overall, brightness appears lower, but the quality of the picture is better to my eyes.
Andy
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post #4 of 91 Old 02-01-2006, 08:34 AM - Thread Starter
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Quote:
Originally Posted by Tryg
This has been reported many times.

3000:1 iris open
5000:1 iris closed
15000:1 auto

So you say that they Ruby, with auto iris, have excactly the same image CR as a projector that have a native CR of 15K:1 on low level scenes? So IRL, a Ruby does as good as a CRT in low level scenes?

I don't know, but I thought I read somewhere about the HS50, that one could take half of the the measured on/off CR in auto iris, and you will have the "true" native CR ratio.

It have been said before many times that auto iris controlled CR is not the same as native CR. So I woulder, what is the "true" on/off CR of the Ruby? Same as HS50, half of the one in auto, or more?


/Mattias

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post #5 of 91 Old 02-01-2006, 08:36 AM - Thread Starter
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Quote:
Originally Posted by Andrew P
I tried Darins tweaks and I noticed an improvement in overall picture quality. I havent measure the numbers per say. Overall, brightness appears lower, but the quality of the picture is better to my eyes.
Andy

What is better? Will dark scenes have better blacks, but bright objects in those scenes looks more dull?

Sound and video is not magic, it is pure physics. Physics that can be magical
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post #6 of 91 Old 02-01-2006, 09:27 AM
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Quote:
Originally Posted by NIN74
What is better? Will dark scenes have better blacks, but bright objects in those scenes looks more dull?
I haven't noticed that affect at all. In fact I find the bright objects to light up very nicely within dark scenes. An excellent example of this is in the Alien Vs. Predator movie. It mostly takes place in dark corridors and tunnels yet all the details and bright parts of the image light up very nicely and there is no haze. Truely remarkable.

The best way I can describe Darin's tweak is that it noticeably increases the depth of the image - makes it even more 3D looking than it already is by default. Also the image looks sharper with even greater detail with this tweak.

While the spec is 15000:1 and has been measured a bit higher by Greg, Darin is reporting close to 30000:1 with his tweak. Whether there is much noticeable difference between 15000: 1 and 30000:1 I cannot say. But I can say for certain dark movies are one of Ruby's best talents.
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post #7 of 91 Old 02-01-2006, 10:40 AM
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Quote:
Originally Posted by NIN74
So you say that they Ruby, with auto iris, have excactly the same image CR as a projector that have a native CR of 15K:1 on low level scenes? So IRL, a Ruby does as good as a CRT in low level scenes?
/Mattias
A contrast ratio is just that a ratio of two numbers. One of those numbers "the black level" will tell you how dark black will be when every pixel on the projector is displaying black. The black level produced by a well calibrated CRT will typically be lower than the Rubys calibrated black level. If a CRT had the same contrast as the Ruby then it's white level (the brightness of an all white scene) would need to be lower. Well, that's a long winded introduction to my point which is this, there are a whole lot of things that go into making a high quality picture and contrast is just one of them. From the sound of it you are trying to use only contrast ratios to determine picture quality in dark scenes. In my opinion that places you on a slippery slope. You need much more information including ANSI contrast and black detail, plus a few descriptive observations like white compression etc. In addition, in dark scenes, the room and screen play a big part in picture quality. The bottom line is everyone is going to place a different importance to all of these things that go into producing a dark scene, which is why Greg's reviews are so valuable he gives you all of the information you need to make an educated guess as to the quality of the picture. Still, there is no substitute for viewing a projector in your environment.

Human perception is not a direct consequence of reality, but rather an act of imagination. - Michael Faraday
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post #8 of 91 Old 02-01-2006, 11:22 AM
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Do we have any numbers for the Ruby's ANSI CR?
Does it change with iris position (open vs. closed?)
I'd be interested to see what effect the iris to the ANSI CR.
I'm also assuming that the Qualia has a better ANSI CR than the Ruby due to better optics.
Is that true?
Darin? :D

Next projector will have LEDs, >=1080 res, >=10 bit color, >14bit CR, >9 bit ANSI CR, >=120Hz, >16ft.L on 12ft 2.35:1 screen, <$12bit price

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post #9 of 91 Old 02-01-2006, 11:26 AM
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Quote:
Originally Posted by Andrikos
Do we have any numbers for the Ruby's ANSI CR?
Does it change with iris position (open vs. closed?)
I'd be interested to see what effect the iris to the ANSI CR.
I'm also assuming that the Qualia has a better ANSI CR than the Ruby due to better optics.
Is that true?
Darin? :D
IIRC Greg published ANSI CR numbers in his Ruby review.
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post #10 of 91 Old 02-01-2006, 12:19 PM
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Quote:
Originally Posted by mdputnam
which is why Greg's reviews are so valuable he gives you all of the information you need to make an educated guess as to the quality of the picture. Still, there is no substitute for viewing a projector in your environment.
That's the bottom line. #'s do NOT tell the WHOLE story. mhafner could not understand that the Mercury HD had better APPEARING blacks than the Ruby in MY environment. I would bet that mhafner could come to my house with his Ruby and prove his point with measurements. I have no arguement about that.

It could very well be some optical illusion due to the picture attributes of the Merc (maybe due to the Merc being brighter and my eyes adjusting-just guessing), but even if it is, it's what my eyes say that matters, not some testing instrument.
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post #11 of 91 Old 02-01-2006, 02:00 PM - Thread Starter
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Quote:
Originally Posted by mdputnam
A contrast ratio is just that a ratio of two numbers. One of those numbers "the black level" will tell you how dark black will be when every pixel on the projector is displaying black. The black level produced by a well calibrated CRT will typically be lower than the Rubys calibrated black level. If a CRT had the same contrast as the Ruby then it's white level (the brightness of an all white scene) would need to be lower. Well, that's a long winded introduction to my point which is this, there are a whole lot of things that go into making a high quality picture and contrast is just one of them. From the sound of it you are trying to use only contrast ratios to determine picture quality in dark scenes. In my opinion that places you on a slippery slope. You need much more information including ANSI contrast and black detail, plus a few descriptive observations like white compression etc. In addition, in dark scenes, the room and screen play a big part in picture quality. The bottom line is everyone is going to place a different importance to all of these things that go into producing a dark scene, which is why Greg's reviews are so valuable he gives you all of the information you need to make an educated guess as to the quality of the picture. Still, there is no substitute for viewing a projector in your environment.

No, maybe I didn't write it as clear as I wanted:

Are the Ruby's 16700:1 CR in iris auto the same as a PJ with a native CR of 16700:1? And what about ANSI in low level scenes with the iris in auto?

Hope this was more clear.


/Mattias

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post #12 of 91 Old 02-01-2006, 03:33 PM
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Quote:
Originally Posted by NIN74
No, maybe I didn't write it as clear as I wanted:

Are the Ruby's 16700:1 CR in iris auto the same as a PJ with a native CR of 16700:1?
Case 1. In a very dark scene with no "bright" objects - yes.
Case 2. When there are "bright" objects in the dark scene - not exactly.
Case 3. In "brighter" scenes - no.

Here's the explanation.

The 16700:1 CR is the ratio of the maximum bright level with the Auto Iris aperture in its most open position to the minimum black level with the Auto Iris aperture in its most closed position. Obviously the aperture can't be in the most open position and most closed position at the same time. Therefore, there can never be a 16700:1 difference between any areas in the same image. BUT,

Case 1. In a very dark image the iris aperture is in the most closed position so the black level is at the minimum. The signal gain is then electronically increased so that dark levels of the image are reproduced with the same brightness they would have had if the aperture were fully open. Therefore, the ratio of the dark areas to black is the same as it would be if the projector had a fixed iris with a 16700:1 contrast ratio. This is critical to the perceived image quality because dark scenes are where a high full-field (on-off) contrast ratio matters the most. It allows you to see dark detail without haziness.

Case 2. Now assume that a few bright (perhaps 50% to 100% signal levels) small objects enter the dark scene in case 1. Perhaps car headlights in the far distance, distant street lights, bright stars in the sky, etc. If the bright objects are small the iris aperture remains at the minimum size and the black level remains at minimum, but the bright objects can never be reproduced at the same brightness they would have been with a maximum open aperture. Moreover, because the signal gain was increased (to increase the brightness of dark signals as explained above) the bright signal levels must be compressed closer together so that none of the bright signals clip at the maximum signal level, else there will be no bright detail differentiation at all above some incoming signal brightness level. Therefore, the image has brightness compression. Plus the brightest areas are not nearly as bright as they would be if the projector had a fixed aperture with a 16700:1 contrast ratio. However, since it is a very dark scene with only a few very bright objects, our eyes still perceive a large difference in brightness between those objects and the rest of the scene and we likely don't perceive that the brightness of those objects should be brighter still. If there are graduations of brightness levels in those objects, those levels are squeezed closer together and our ability to discern the detail in bright areas is reduced. But since the objects are small we are less likely to notice that degradation in image quality. So to sum up case 2, we still get the same benefit of a fixed iris 16700:1 CR in the darker areas of the image, but there is some image degradation in small bright objects that may not be particularly evident.

Case 3. If the overall image is brighter the iris aperture opens up to some value between minimum and maximum. In that case the black level increases so we can no longer have the benefit of a fixed iris 16700:1 full-field contrast ratio. However, there must be less black area and more brighter areas in the image (else the aperture wouldn't have opened up) so the full-field contrast ratio is less important to the image quality and the intrafield contrast ratio becomes an issue. More importantly, brightness compression becomes a bigger issue because the incoming signal must still be compressed to avoid clipping, and there are more, larger bright areas in the image where we may perceive lost brightness detail.

Eventually as the average image brightness increases the aperture opens larger and we need less signal compression. Finally with very bright images, the aperture opens to the maximum size and no signal compression is used. At that point the full-field contrast ratio is equivalent to the Iris Off CR of about 3,000:1, but since there is very little black or dark areas in the image the full-field CR doesn't matter.

Note that by decreasing the minimum aperture size further (i.e. increasing the ratio between the maximum and minimum iris aperture size) the full-field CR can be increased further, but the brightness limiting (i.e. the perception of maximum brightness in very dark scenes) gets worse and brightness compression effects are increased.

Greg Rogers
Video Engineer/Product Designer

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post #13 of 91 Old 02-01-2006, 04:00 PM
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Quote:
Originally Posted by gregr
Case 1. In a very dark scene with no "bright" objects - yes.
Case 2. When there are "bright" objects in the dark scene - not exactly.
Case 3. In "brighter" scenes - no.
With the eye having an auto iris but only an instance dynamic range of 100 (iris not changing), do these cases have any relevance to what we actually see.

There is also a chemical adaption of intensity by the eye when the eye moves. Maybe that could take more advantage of the cases, but I don't know
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With the eye having an auto iris but only an instance dynamic range of 100 (iris not changing), do these cases have any relevance to what we actually see.
]


WARNING! WARNING! Erroneous 100:1 contrast ratio ability number!

We can see a lot more than 100:1 at any one time, so yes the iris has a visible impact in cases #2 and 3. the question is how much is that worth to you over having a crappy looking elevated black in case #1. This will dictate how extreme you'd want the iris to "expand" the CR range dynamically.
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post #15 of 91 Old 02-01-2006, 06:17 PM
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Quote:
Originally Posted by ChrisWiggles
]


WARNING! WARNING! Erroneous 100:1 contrast ratio ability number!

We can see a lot more than 100:1 at any one time.
How much more?

What is the instantaneous CR of the human eye?
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post #16 of 91 Old 02-01-2006, 06:26 PM
 
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I don't know, but it's much MUCH more than 100:1.

The 100:1 number seems to come (as Darin has explained in the past) from erroneous confusion of CSF numbers, where one can discern a difference of about 1% in luminance, or 1 to 1.01 which can be expressed as 1:100. This is *completely* different thatn a contrast ratio which attempt to describe the maximum difference we can see at one time, rather than the minimum difference. CSF attempts to describe (among other things) more like a white sheet of paper against a white wall, and whether you see that as the same or different. This is very different than a white sheet of paper on a black wall, where the difference is an extremely large amount.

When dealing with the difference, or a ratio between white and black, there are many numbers thrown about, but I believe the guys at Brightside said 100,000:1 at any one time, and 10^14 total as the iris adjusts.
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post #17 of 91 Old 02-01-2006, 06:28 PM
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Quote:
Originally Posted by HoustonHoyaFan

What is the instantaneous CR of the human eye?
Seriously, who cares. How many tablespoons of water are there in the Pacific Ocean? 12,345,654,765,445,876,765,876,456,765,456,756,876,978 or
12,345,654,765,445,876,765,876,456,765,456,756,876,964?

There are some who say "true" 2000 CR of certain projectors look truer than others. BULL*****! The instruments dont lie. Only those pushing the products like to bring up these nonsense arguments.

As we ease past 5000:1 CR numbers is there really any point in arguing about these numbers anymore? especially for people who haven't even seen a projector that can do this. :rolleyes:
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I think it's a very important question, because it gets at the question of how much ANSI contrast is important. Sadly, this 100:1 number is paraded around, as if 100:1 ANSI CR is all you need because that's all you can see. This is horribly wrong as experience will show you. The 100,000:1 number gives you an idea of how large a range we really can see. This is probably a maximum extreme, because this will vary depending where your gaze is directed. As you approach a high-contrast boundary, this will decrease greatly. But still, it's quite impressive. As has been said before, the 100:1 number is ridiculous, because nobody here would be able to drive at night if this were the limit of human capabilities.
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post #19 of 91 Old 02-01-2006, 07:12 PM
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I was disappointed in a viewing of the Ruby. The material was a rock concert, with generally dark scenes that have some very bright objects. These scenes were displayed with the bright objects appearing quite dull. [Iris in auto mode.]

Exactly what Greg Rogers and others suggest, but it appeared to me to be a very serious limitation.

I caution that the demo was likely not well set up.
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post #20 of 91 Old 02-01-2006, 07:18 PM
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Quote:
Originally Posted by NIN74
So you say that they Ruby, with auto iris, have excactly the same image CR as a projector that have a native CR of 15K:1 on low level scenes? So IRL, a Ruby does as good as a CRT in low level scenes?
Greg covered a lot of this, but I wanted to mention that I think most CRTs are setup to much higher on/off CRs than I had thought. A friend and I will do more testing between a Ruby, a G70 and using neutral density filters, but at this point I think his on/off CR as setup with his PC (with a little gamma tweak at the bottom) is probably in the multiple hundreds of thousands. Basically, I need to measure the on/off CR of the Ruby, see how much neutral density material it takes to get the white levels about the same and then about how much it takes to get the absolute black levels about the same. I haven't done this with precision, but with some ND material I had with me the last time I was down there I think that G70 will end up at 10x or more the on/off CR of the Ruby. For anybody wondering, the reason I am taking this approach is because I think our eyes are much more accurate than my measuring equipment at this extreme.

--Darin

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post #21 of 91 Old 02-01-2006, 07:48 PM
 
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Darin: that's very interesting to hear. I'd definitely be interested to learn what you and steve come up with with those experiments.
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post #22 of 91 Old 02-01-2006, 08:54 PM
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Quote:
Originally Posted by gregr
...Note that by decreasing the minimum aperture size further (i.e. increasing the ratio between the maximum and minimum iris aperture size) the full-field CR can be increased further, but the brightness limiting (i.e. the perception of maximum brightness in very dark scenes) gets worse and brightness compression effects are increased.
I believe this is exactly what Darin achieved with his posted factory menu tweaks, which causes the iris to clamp down further in dark scenes and open wider at the top end. Darin - do you think that is the case?

I'm a big fan of this tweak. I still am not noticing any significant brightness compression, I do not notice a maximum brightness in dark scenes to be any darker than without the tweak, and Darin reported close to 30,000:1 CR with this tweak. IMO the image is much more dramatic with significantly more depth. In one case I actually felt my stomach turn as the camera panned over the edge of a building.

Greg thanks so much for taking the time to explain that. It was a fascinating read.
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post #23 of 91 Old 02-02-2006, 01:47 AM
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Quote:
Originally Posted by Staged
That's the bottom line. #'s do NOT tell the WHOLE story. mhafner could not understand that the Mercury HD had better APPEARING blacks than the Ruby in MY environment. I would bet that mhafner could come to my house with his Ruby and prove his point with measurements. I have no arguement about that.
Sure I can understand. Can you understand that the Mercury does not have lower black level (measured and apparent) when you calibrate to the same white level as the Ruby and watch suitable material?
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post #24 of 91 Old 02-02-2006, 03:21 AM
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darinp2
Do you need a lower black level and a higher on off sequentially than what the gamma tweaked G70 can offer?

My conclusion is that SLM-based projectors will give us everything but fade to black with some minor faults. The only way to get the fade to blacks perfected is to shut off the light source. We need a light source that can be totally or close to totally off and then on again in a fraction of a second. I think I have said this too often.

gmgav´s find
GLV has been a distant promise but bad contrast news has made GLV a grayer prospect. Recent news about GLV in a paper claims cr >10000:1. If the lasers are set to close to off I think it could fake black for a couple of seconds.
http://bookstore.spie.org/index.cfm?...=645463&coden=

Future SLM technology + led/laser
native 10000:1
ANSI 400:1?
on off: 10000-infinity

With the rate of progess with sxrd I can see sxrd hitting native 10000:1. The biggest obstacle in development for sxrd is probably dark uniformity and not ultra high contrast.

Mattias Ohlson
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post #25 of 91 Old 02-02-2006, 04:18 AM
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Quote:
Originally Posted by mhafner
Sure I can understand. Can you understand that the Mercury does not have lower black level (measured and apparent) when you calibrate to the same white level as the Ruby and watch suitable material?
I understand what the #'s mean and what the measurements would be with all other things being equal. No arguement from me about that. I don't agree that all measurements will ALWAYS equal the same truth/measurements during subjective viewing to every person. There is no absolute truth with anything "subjective", except to the person voicing their subjective opinion. Remember not all of the other things were equal in my viewing. It was not a scientific test. It was a real world subjective test, in MY real world environment, and in a few long demos at the a/v store.

mhafner, I agree with your scientific points. They are logical.
What I don't agree with, is all of the talk with how those #'s translate into some "otherworldly performing projector" which has no rival and due to these HUGE #'s difference it's IMPOSSIBLE for another projector to at least APPEAR in certain environments to perform better in those subjective areas.

It wasn't that close. Keep in mind..my living room is not a bat cave and although it has total light control, the walls are light colored. Just putting that point out there as maybe it has something to do with it when I viewed it at my house. I don't know...

When I did view the Ruby in a bat cave, it was not back to back with any other projector since I didn't feel like dragging mine to the store.

I'm not saying that makes me or the other people with me (one of whom's agenda was for me to KEEP the Ruby) right, and that everyone should agree with what we saw, in terms of APPARENT black level or any of our other conclusions in terms of picture quality. But just because you can measure something in certain conditions with a certain tool doesn't mean it will hold true in ALL conditions, and with a DIFFERENT measuring tool; a human eye. Nor does it automatically translate into a 300% real world improvement in that area.

I am positive that in other environments, the Ruby would be in the position of subjective victor over both of the projectors I compared it to. No doubt at all...
Also, remember, I am not talking about price. $ for $, my opinion is that the Ruby is the best value by a long shot.

Everyone is best served to see all projectors they are interested in themselves, in their environment (room, screen, etc), and make their own conclusions... and be happy.:) Use the posts here and the reviews to help narrow down your choices, but DEMO them.

mhafner: I do not mean any offense with any of my posts. so apologies in advance if I came across that way.
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post #26 of 91 Old 02-02-2006, 05:37 AM - Thread Starter
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Greg, thanks for the explanation!


darinp2, and want to know more about your tweaks and what you think these will do for low level scenes. Are these 30000:1 value anything "real"? Like I said again, in low level scenes with some bright objects, would these tweaks behave like like a native 30000:1 PJ?

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post #27 of 91 Old 02-02-2006, 09:42 AM
 
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A DI cannot make a projector behave completely like a display that has a native 30,000:1 CR because the CR at any given iris position is much smaller than that. This is why it depends on what's in the scene. If what's in the scene is all very dim, it will look like the 30K native because a 30K native machine would only be using a small part of its dynamic range capability, and if that small part is small enough to "fit inside" the momentary static range of CR of the DI projector, then they will be the same. But if you have a lot of black, and some bright highlights, that image range could easily exceed the static contrast range of the DI projector.
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post #28 of 91 Old 02-02-2006, 10:50 AM
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Quote:
Originally Posted by NIN74
darinp2, and want to know more about your tweaks and what you think these will do for low level scenes. Are these 30000:1 value anything "real"? Like I said again, in low level scenes with some bright objects, would these tweaks behave like like a native 30000:1 PJ?
I haven't completely calibrated and then measured and so the center may end up with less CR than that. The corners do have lower CR than the center on this one (maybe half). You have a Ruby yourself so please just try the tweaks (140 for #43 and 700 for #44) with different scenes and see what you think. If you don't save them to memory they will go back to their defaults when you turn the projector off and back on, but you should write down the current values anyway. And you can always put them back before turning the projector off if you want.

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post #29 of 91 Old 02-02-2006, 11:24 AM
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Quote:
Originally Posted by ChrisWiggles
A DI cannot make a projector behave completely like a display that has a native 30,000:1 CR because the CR at any given iris position is much smaller than that. This is why it depends on what's in the scene. If what's in the scene is all very dim, it will look like the 30K native because a 30K native machine would only be using a small part of its dynamic range capability, and if that small part is small enough to "fit inside" the momentary static range of CR of the DI projector, then they will be the same. But if you have a lot of black, and some bright highlights, that image range could easily exceed the static contrast range of the DI projector.
Yes, and the key benefit here of course is that the very high CR (presumably 15,000:1 or much higher based on tweaks) is really only necessary for the dark scenes. In the brighter scenes you effectively have much less CR, but super high CR in those scenes is much less important. That's why the DI works out so nicely IMO.
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post #30 of 91 Old 02-02-2006, 01:26 PM
 
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Absolutely!
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